An aircraft is propelled by a number of jet engines each housed in a nacelle which also houses a collection of ancillary actuating devices associated with operation thereof, such as a thrust reverser device, and which performs various functions when the jet engine is running or shut down.
A nacelle generally has a tubular structure comprising an air intake upstream of the jet engine, a median section intended to surround a fan of the jet engine, a downstream section housing thrust reverser means and intended to surround the combustion chamber of the jet engine, and generally ends in a jet pipe the outlet of which is situated downstream of the jet engine.
Modern nacelles are designed to house a bypass jet engine capable, via the blades of the rotating fan, of generating a stream of hot air (also known as the primary stream) that comes from the jet engine combustion chamber, and a stream of cold air (the secondary or bypass stream) which flows around the outside of the jet engine through an annular passage also known as a duct, formed between a jet engine cowling (or an internal structure of the downstream structure of the nacelle and surrounding the jet engine) and an internal wall of the nacelle. The two air streams are ejected from the jet engine at the rear of the nacelle.
Each power plant of the aircraft is therefore formed of a nacelle and of a jet engine, and is suspended from a fixed structure of the aircraft, for example under a wing or on the fuselage, by a pylon or strut attached to the jet engine or to the nacelle.
The nacelle is generally fitted with mobile cowls which can open to provide access to the jet engine during maintenance operations. These mobile cowls are generally situated in the median section surrounding the fan or gas generator of the jet engine where they may incorporate a thrust reverser device.
Usually, these cowls have a curvature tailored to the surroundings of the jet engine allowing it to fit into the nacelle and ensuring its aerodynamic continuity in the closed position. They are generally attached to the pylon that supports the nacelle by attachment means allowing them to be articulated about an axis substantially parallel to a longitudinal axis of the nacelle and having a lower edge equipped with locking means able to keep them in the closed position during flight operations. The operation of opening the cowls is performed once the locking means have been opened up by pivoting them about the attachment means secured to the pylon.
The pylon thus acts as a bearing fixed structure for the pivot axes about which the cowls are articulated.
However, in certain aircraft power plant configurations, there is no fixed structure available above the nacelle to act as a support for the pivot axes about which the mobile cowls are articulated. It then becomes difficult, if not impossible, to access the jet engine without, for example, having to resort to cumbersome maintenance tooling to remove the mobile cowls.